Many boats and other watercraft are propelled by one or more outboard engines disposed at the rear of the watercraft, which drive one or more propellers. Many different sizes of outboard engines are available, ranging from below 1 horsepower to over 350 horsepower, depending on the size of the watercraft to be powered and the power requirements of the user. During operation, a number of aspects of the operation of the outboard engine may be controlled by the user, depending on the particular outboard engine, such as starting and stopping the engine; throttle; tilt; trim; steering; shifting between forward, neutral and reverse modes; and the pitch of the propeller.
Larger outboard engines (e.g. above 30 horsepower) are typically used with larger and more sophisticated watercraft, which have electrical connections and controls for the outboard engine provided on the watercraft, often at a location remote from the outboard engine, such as a steering wheel or handlebar disposed at the front of the watercraft. Small and medium sized outboard engines (e.g. below 30 horsepower) are often used on watercraft without separate controls, and are typically controlled by a user positioned close to the outboard engine while the outboard engine is in operation. The user steers the watercraft by using a tiller arm to pivot the engine with respect to the watercraft about a vertical steering axis, and controls other aspects of the operation of the engine via controls mounted either on the tiller arm or on the outboard engine itself.
Referring to FIG. 1, a conventional tiller arm 10 includes an elongate tiller arm body 12 with a U-shaped cross-section, made of cast aluminum. Mechanical or electrical connections 14 are disposed inside the U-shaped cross-section to connect the throttle grip 16 and other controls 18 to the engine, either via an electronic control unit (ECU) (not shown) or via a mechanical linkage. A bottom cover (not shown), usually made of plastic, is optionally provided to conceal the mechanical or electrical connections 14 for aesthetic purposes. The user can move the tiller arm 10 to physically orient the engine as desired, for example to steer the watercraft. The user may also use the controls 16, 18 disposed on the tiller arm 10 to control the operation of the outboard engine. The number and type of controls disposed on the tiller arm 10 depend on the size and sophistication of the outboard engine. The tiller arm 10 can be pivoted relative to a raised position to provide additional space inside the watercraft when the engine is not in use. The tiller arm 10 can also be raised to provide a compact arrangement for transporting the outboard engine when it is detached from the watercraft, for example for maintenance or relocating from one body of water to another.
While conventional tiller arms are generally adequate for operating outboard engines, they have a number of drawbacks. In order to allow steering of the outboard engine, the tiller arm must withstand the forces required to physically rotate the outboard engine about the steering axis while the outboard engine is in operation. The force required is greater for a larger and more powerful outboard engine, necessitating a larger, stronger and heavier tiller arm. As a result, bulk and weight are added to an already large engine, resulting in diminished performance of the watercraft to which the outboard engine is mounted, and making transportation of the outboard engine cumbersome. A larger tiller arm may also be difficult for a user to grip with his hands, adding to the difficulty in transporting the outboard engine.
In addition, large tiller arms are costly to manufacture, due to their increased size and the increased quantity of aluminum and other materials required. Adding or removing even minor features of a cast aluminum tiller arm, for example to make ergonomic modifications or add or remove controls, may require replacing the mold used in the casting process, which represents a significant additional expense and discourages improvements to existing designs.
In addition, some users consider a large and bulky tiller arm to be aesthetically displeasing. However, such large and bulky tiller arms may be required to physically steer an engine that is large enough to satisfy the user's power requirements but still small enough to be used on a watercraft without separate steering and engine controls.
Plastic and composite tiller arms address some of the above concerns. However, due to the lower structural rigidity of plastic compared to aluminum, plastic tiller arms are currently used only on the smallest of outboard engines, typically those below 10 horsepower.
Therefore, there is a need for a tiller arm having reduced manufacturing cost.
There is also a need for a tiller arm having increased structural rigidity and reduced weight.
There is also a need for a tiller arm allowing for inexpensive design modifications.
There is also a need for a tiller arm allowing for easier transportation of an outboard engine to which it is attached.